AFUE

damper:
HVAC Duct system

damper:
barometric

direct exhaust appliance

direct vent appliance

forced draft

induced draft

mechanical draft

natural draft

stack effect

flue

hydronic heating

mainfold vent connector

combustion vent

vent connector

vent system

flue collar

combustion air

primary air

dilution air

net free area

standard method
gas appliance

inside air
adjacent rooms
gas appliance

inside air
different stories
gas appliance

combustion air same room
oil furnace

inside air adjacent rooms
openings
oil furnace